The present invention relates to a plasma monitoring method and a plasma monitor for measuring the distribution of the densities of a specified chemical species of molecules, atoms, ions or the like contained in a plasma, in a processing step utilizing the plasma such as sputtering and dry etching.
In the production of an LSI or a very LSI, it is required to arrange minute circuit pattens, the line widths of which are below several .mu.m or below .mu.m, at a high density. Therefore, wet processes such as plating and etching with a chemical solution are being switched over to dry processes capable of minute processing, such as dry etching and sputtering.
In order to precisely perform the minute processing with the dry process, it is necessitated to restrain fluctuations in processing conditions and to monitor the progress of the processing. To this end, several monitors have been proposed which monitor the progress of the processing by exploiting the light emission of a plasma generated during the dry process.
For example, in a monitor for dry etching, the quantity of light emission of the whole plasma generated during the processing and the quantity of light emission of an etching substance contained in the plasma are measured by individual measurement means, and the results are compared, whereby the density of the etching substance contained in the plasma is found so as to detect the end point of the etching.
In a monitor for sputtering, the quantities of light emission of two chemical species among chemical species constituting the plasma generated during the processing are measured by individual measurement means, and the results are compared, whereby the rate of the sputtering or the composition of a film to be formed is predicted.
Since these monitors measure the light emission of the whole plasma (or a part of the plasma) to be monitored, they merely grasp the state of the whole plasma (or the part of the plasma).
It is therefore impossible to grasp dispersion in the progress of the processing within a processing region. This signifies that, in the case of the dry etching, the degree of etching becomes excessive or insufficient, while in the case of the sputtering, dispersion in the thickness or composition of the formed film occurs inevitably. It is also impossible to obtain information for keeping the uniformity of processing within an identical lot or the reproducibility of a processed state among lots.
Further, since the two detection means are employed, the apparatus becomes high in cost and large in size. Another disadvantage is that errors develop due to the difference of the sensitivities of the respective detection means and the difference of the received quantities of light attributed to the difference of the positions where the respective detection means are arranged. The monitors have such numerous disadvantages.